1. Field of the Invention
The present invention relates to a charge-coupled amplifier, which has a combined faculty of an analog shift register and a differential amlifier for amplifying a level difference between two signals with a favorably stable gain.
2. Description of the Prior Art
A conventional wide band differential amplifier having a favorably stable gain is formed mostly by such a means that a differential amplifier having a high gain in an open-loop condition is negatively fed back, so that the drift of the gain in the open-loop condition does not affect significantly the total gain of the differential amplifier. In this case, it is required that the gain in the open-loop condition be sufficiently high, and that the phase characteristics of the differential amplifier be so good that an oscillation does not occur in spite of the feed-back which is enough to obtain good stability. For reasons mentioned above, the conventional wide band and favorably stable differential amplifier is quite complicated. Besides, it is required that circuit elements used for it have good frequency characteristics, and consequently it is very difficult to utilize monolithic type integrated circuits having unfavorable frequency characteristics form a differential amplifier for use in the video frequency band.
Furthermore, to form a conventional device which can be used as an analog shift register as well as a differential amplifier, it is required to combine an appropriate switching means and an appropriate analog memory with the differential amplifier mentioned above. For instance, such a devicce is shown in FIG. 1. That is, an analog shift register 1 controlled by clock pulses CK as a charge-coupled device (C.C.D.) is connected to one of the input terminals of a differential amplifier 2, and has applied thereto a signal A (t) which is sample-held by a sample-holder 3. The shift register 1 then applies an output sample-held signal A(t-d) shifted by a constant interval d to one of the input terminals of the differential amplifier 2. Another sample-holder 4 is connected to the other one of the input terminals of the differential amplifier 2, and then applies another sample-held signal B(t-d) to the other input terminal. In this way, a differential signal between the two sample-held signals A(t-d) and B(t-d) is derived from the differential amplifier 2. Accordingly, it can be seen that the conventional device mentioned above is quite complicated.